In existing audio and video synchronization detection methods, as black video is played and displayed on a playing device, audio signals with a specific frequency are played. A white video is suddenly played and displayed, and a testing device, for example, an oscilloscope, is used to measure a time difference between the white videos and the audio signals. When the white videos and the sound signals enter the testing device, two time differences are detected, for example, ΔT1 and ΔT2 shown in FIG. 1, where ΔT1=Video1−Audio and ΔT2=Video2−Audio. However, the two time differences need to be checked to determine which time difference is true.